The present invention relates to an automatic device for replacing the printing cartridges in a gravure printing machine.
More particularly, the present invention relates to a device allowing the speed of replacement of the printing cartridges of a gravure printing machine to be remarkably increased, whereby said machine can rapidly be adapted in order to carry out a new printing cycle.
A gravure printing machine comprises a base supporting a roll from which a band made of a relatively flexible material, e.g. a plastic film, or paper, or a light cardboard, is unwound and fed to a plurality of printing stations which are serially placed in respect of said roll and finally rewound on a second roll.
Each printing station is constituted by a frame carrying a plurality of rollers, at least one of them being an impression roller that cooperates with the side surface of a printing cylinder.
The side surface of said printing cylinder is provided with a series of alphanumeric indications and/or raised shapings acting as gravure printing matrices.
In operation, the printing cylinder is partially immerged within an underlying ink tray, and it is disassembled from the printing station together with said ink tray when the printing cycle has to be changed, whereby another printing cylinder bearing different alphanumeric indications or raised shapings is then placed within the printing station in order to obtain a different printed pattern on the advancing tape.
During the printing cycle the band unwound from the first roll is successively fed to the printing rollers of the first printing station, in which the band is driven between the respective printing cylinder and impression roller, whereby a given alphanumeric indication or a graphic pattern is gravure-printed on the band by means of the ink draught from a respective ink tray.
Thereafter, the band is driven to the second printing station, wherein it is subjected to a similar printing procedure, and so on for all the printing stations; the band is finally rewound on said second roll.
Each ink tray, together with its respective printing cylinder, is normally defined as printing cartridge.
In the upper portion of each printing station there is a respective drying hood inside of which the ink that has just been deposited on the film is dried, in such a way that the film can be driven to the subsequent printing station without any risk of smears due to an ink that is on a liquid state yet.
The supporting frame for the rollers and for the printing cylinder may be shaped as a portal or provided with cantilevered elements in such a way that the respective base can easily be accessed in order to drive within the printing station a trolley suitable for supporting a respective printing cartridge.
In operation, the latter is raised on the trolley to reach a working position close to the rollers by means of a mechanical device, and it is lowered to a resting position before drawing the trolley out of its respective printing station.
This known machine involves a major drawback that is constituted by the replacement operation of all the printing cylinders that has to be carried out when the gravure printing machine has to be adapted to perform a new printing cycle.
This operation is manually carried out, and it requires the machine to be stopped for relatively long periods of time, even some hours; consequently, the costs due to the machine stop are considerably high.
The present invention aims to provide for an automatic device for replacing the printing cartridges of a gravure printing machine, in order to substantially reduce the cartridge replacing time.
This is achieved by means of an automatic device for replacing printing cartridges to be used in cooperation with a gravure printing machine comprising a plurality of printing stations, each printing cartridge including an ink tray and a printing cylinder and being supported by a trolley that is provided with a mechanism for selectively raising and/or lowering said printing cartridge to and from a working position inside of a each of said plurality of printing stations of said gravure printing machine, wherein the automatic device comprises: a series of panels housed within a cavity placed close to said plurality of printing stations, said panels having an upper surface that is long enough for supporting at least two trolleys suitable for carrying said printing cartridges; a device for displacing said panels along a direction that is parallel to the longitudinal axis of said machine; a device for displacing said trolleys in a direction that is perpendicular to said longitudinal axis of said machine, in order to carry out a reciprocating movement of the trolleys to and from the respective printing stations.
The dependent claims outline advantageous forms of embodiment of the automatic device according to the present invention.
The automatic device for replacing the printing cartridges of a gravure printing machine according to the present invention comprises:
a longitudinal cavity suitable for receiving a series of panels to be placed close to a printing station, said panels being provided with a longitudinal extension able to support at least two trolleys suitable for carrying printing cartridges;
a device for longitudinally translating said panels;
a printing station provided with a frame fixed to a base and having a side access for inserting and removing a respective trolley;
a device for transversally translating each trolley on guiding means;
an unit for vertically displacing a printing cartridge, suitable for displacing said cartridge from a rest and replacement position, close to the trolley, to a working position, away from said carriage and close to a series of rollers supported by the printing station frame.
According to the invention, the upper surface of the panels is flush with the floor surface.
The device may be provided with detectors which can electrically be connected to an electronic control center that is suitable for controlling and governing both the cartridge replacement and the printing cycle operations.
While the gravure printing machine provided with the automatic device according to the invention is working according to a given printing cycle, a trolley supporting a new printing cartridge, that is provided with a new printing cylinder and a new ink tray, is placed on each panel, next to a respective printing station, said new cartridge being intended for use during a successive printing cycle.
When the printing cartridges have to be replaced, the trolleys which are present inside the printing stations are automatically removed all together, and they are placed on the upper surface of the panels. Thereafter, the panels are longitudinally displaced in such a way that each new trolley is aligned to the access opening of each printing station, and they are then inserted within the respective printing stations.
Each printing station is provided with electrical and pneumatical connectors suitable for feeding the devices which are present on each trolley. When arriving at the end of their run inside the printing station, each trolley is then automatically connected to said electrical and pneumatical connectors, so that it can immediately be operated.
Meanwhile, the trolley which are present on the panels are manually or automatically removed therefrom and they are driven to suitable washing stations.
Therefore, the replacement operation is carried out in an automatic way.
Each printing station is simultaneously fed with a fresh printing cartridge, thereby reducing the machine stop times, incresasing the productivity and reducing the working costs.